The present application relates generally to a chopper assembly for a combine. The present application relates more specifically to a system to determine the position of a counter knife bank in a chopper assembly.
Harvesting equipment, such as agricultural combines, can use integral chopper assemblies or systems to transport material away from the threshing system and to also treat the material, e.g., by further cutting the material, as it is being transported away from the threshing system. A rotary chopper element or portion of the integral chopper system can be operated at or near 3000 revolutions per minute (RPM) to transport the material from the threshing system to a spreading system. When operated at 3000 RPM, the material is transported with the shortest mean length of cut to permit modern minimum tillage applications. In a less common embodiment, the integral chopper system can be operated at a speed of about 800 RPM to more gently transport the material from the threshing system to a spreading system and with considerably less chopping activity. When operated at 800 RPM, the material can be transported to the spreading system with the longest length and least amount of damage.
Integral chopper systems can have a residue chopper assembly that has a rotary chopper component or element disposed laterally within a housing extending generally horizontally across the flow path of the crop residue through the housing, as well as a counter knife assembly extending generally parallel to and spaced from the rotary chopper element. The counter knife assembly has included a chopper grate assembly spaced below and extending generally parallel to the rotary chopper element and a knife mounting assembly positioned generally beneath the chopper grate assembly.
Often, the counter knife assembly can have an adjustment mechanism that is operable to vary the spacing between a grate portion of the chopper grate assembly and the knife mounting assembly, as well as the degree of projection of the blade elements of the knife mounting assembly through the slots of the grate portion. The adjustment mechanism can be operated to move the knife mounting assembly between a fully engaged or inserted position with the blade elements of the knife mounting assembly extending through the slots towards the rotary chopper element and a fully retracted position in which the blade elements are fully withdrawn or retracted from the slots. In addition, the adjustment mechanism can move the blade elements to various positions between a fully engaged position and a fully retracted position.
When the knife mounting assembly is in an engaged position, either fully or partially, the crop residue can be chopped into smaller pieces by the cooperative actions of the knife blades or elements of the knife mounting assembly and the knife blades or paddles on the rotating rotary chopper element as the crop residue is moved and propelled rearward. The knife mounting assembly is usually positioned into an engaged position, either fully or partially, when the rotary chopper element is operated at or near 3000 RPM and is usually positioned in a fully retracted position when the rotary chopper element is operated at 800 RPM to avoid excessive power requirements for the combine. In addition, different types of crop material may have different desired chopping requirements. Thus, it would be desirable to know the position of the knife mounting assembly to avoid excessive power requirements when operating the chopper system at lower speeds, e.g., 800 RPM, and to confirm that the crop material is being cut as desired.
One example of a system for determining the position of the knife mounting assembly is disclosed in U.S. Pat. No. 7,648,413. As described in the patent, a sensor is placed in association with the knife blades of the knife mounting assembly to provide a signal representative of the position of the knives. Since the sensor is positioned in direct association with the knives, the sensor requires precise calibration to make an accurate measurement of the position of the knives and is susceptible to damage from crop residue.
Therefore, what is needed is a system that can accurately determine the position of the counter knife bank in a chopper assembly without being susceptible to damage from material passing through the chopper assembly.